A storage device, known as a hybrid drive, has two different types of nonvolatile memories, such as a magnetic disk and an NAND type flash memory. The magnetic disk is operated at a lower access speed, but is less expensive. On the other hand, the NAND type flash memory is more expensive, but can be operated at a faster access speed. For this reason, the hybrid drive is able to cancel out disadvantages of the magnetic disk and the NAND type flash memory with each other.